这是一个完整，然后说哪些有用
adapter = object : BAdapter<ActivityViewHolder, JSONObject>(R.layout.item_show_print_list, data) {
var lruCache: LruCache<String, BitmapDrawable>? = null
init {
val cacheSize = 1024 * 1024 * 1024 / 8
lruCache = object : LruCache<String, BitmapDrawable>(cacheSize) {
override fun sizeOf(value: String?, key: BitmapDrawable?): Int {
return key!!.getBitmap().getByteCount()
}
};
}
fun addBitmapToMemoryCache(key: String, drawable: BitmapDrawable) {
if (getBitmapFromMemoryCache(key) == null) {
lruCache!!.put(key, drawable)
}
}
fun getBitmapFromMemoryCache(key: String): BitmapDrawable? {
return lruCache!!.get(key)
}
inner class BitmapWorkerTask(private val mImageView: ImageView?) : AsyncTask<String, Void, BitmapDrawable>() {
override fun doInBackground(vararg params: String): BitmapDrawable {
val imageUrl = params[0]
// 在后台开始下载图片
val bitmap = downloadBitmap(imageUrl)
val drawable = BitmapDrawable(App.getContext().resources, bitmap)
addBitmapToMemoryCache(imageUrl, drawable)
return drawable
}
override fun onPostExecute(drawable: BitmapDrawable?) {
if (mImageView != null && drawable != null) {
mImageView.setImageDrawable(drawable)
}
}
/**
* 建立HTTP请求，并获取Bitmap对象。
*
* @param imageUrl 图片的URL地址
* @return 解析后的Bitmap对象
*/
private fun downloadBitmap(imageUrl: String): Bitmap? {
var bitmap: Bitmap? = null
var con: HttpURLConnection? = null
try {
val url = URL(imageUrl)
con = url.openConnection() as HttpURLConnection
con.connectTimeout = 5 * 1000
con.readTimeout = 10 * 1000
bitmap = BitmapFactory.decodeStream(con.inputStream)
} catch (e: Exception) {
e.printStackTrace()
} finally {
con?.disconnect()
}
return bitmap
}
}
override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): BAdapterViewHolder {
val view = LayoutInflater.from(parent!!.context)
.inflate(resource, parent, false)
return ActivityViewHolder(view)
}
override fun onBindViewHolder(p0: BAdapterViewHolder, position: Int) {
val get = data.get(position)
val holder = p0 as ActivityViewHolder
val nextInt = Random().nextInt()
holder.tv_item1.setText("溯源码" + nextInt)
holder.tv_item2.setText("品牌：草原牧业")
holder.tv_item3.setText("名称：牛小排")
holder.tv_item4.setText("价格22元/kg")
var url: String = imgData.get(Random().nextInt(imgData.size))
val drawable = lruCache?.get(url)
if (drawable != null) {
holder.iv_pic.setImageDrawable(drawable)
} else {
val task: BitmapWorkerTask = BitmapWorkerTask(holder.iv_pic);
task.execute(url);
}
holder.mView1.setOnClickListener(object : View.OnClickListener {
override fun onClick(p0: View?) {
LAST_LINE_TEXT_PLACE_Y = dp2px(115)
QRCStr = nextInt.toString()
initPlace("溯源码" + nextInt, "溯源码", "品牌：草原牧业", "名称：牛小排", "价格22元/0kg")
btnLabelPrint()
}
})
}
}
rv.layoutManager = LinearLayoutManager(this)
rv.itemAnimator = DefaultItemAnimator()
rv.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))
rv.adapter = adapter
bt_lanya.setOnClickListener(object : View.OnClickListener {
override fun onClick(p0: View?) {
btnBluetoothConn()
}
})这个东西用来缓存图片，把图片和图片链接结合起来，为防止错位做准备
var lruCache: LruCache<String, BitmapDrawable>? = null
init {
val cacheSize = 1024 * 1024 * 1024 / 8
lruCache = object : LruCache<String, BitmapDrawable>(cacheSize) {
override fun sizeOf(value: String?, key: BitmapDrawable?): Int {
return key!!.getBitmap().getByteCount()
}
};
}把图片保存到缓存里
fun addBitmapToMemoryCache(key: String, drawable: BitmapDrawable) {
if (getBitmapFromMemoryCache(key) == null) {
lruCache!!.put(key, drawable)
}
}从缓存得到图片
fun getBitmapFromMemoryCache(key: String): BitmapDrawable? {
return lruCache!!.get(key)
}用来后台下载图片，并把图片缓存进缓存，然后设置图片你，这个类是从零开始下载图片，然后加进 缓存，然后设置图片到view
标记一下，这下面的是下载代码，也是下载类
inner class BitmapWorkerTask(private val mImageView: ImageView?) : AsyncTask<String, Void, BitmapDrawable>() {
override fun doInBackground(vararg params: String): BitmapDrawable {
val imageUrl = params[0]
// 在后台开始下载图片
val bitmap = downloadBitmap(imageUrl)
val drawable = BitmapDrawable(App.getContext().resources, bitmap)
addBitmapToMemoryCache(imageUrl, drawable)
return drawable
}
override fun onPostExecute(drawable: BitmapDrawable?) {
if (mImageView != null && drawable != null) {
mImageView.setImageDrawable(drawable)
}
}
/**
* 建立HTTP请求，并获取Bitmap对象。
*
* @param imageUrl 图片的URL地址
* @return 解析后的Bitmap对象
*/
private fun downloadBitmap(imageUrl: String): Bitmap? {
var bitmap: Bitmap? = null
var con: HttpURLConnection? = null
try {
val url = URL(imageUrl)
con = url.openConnection() as HttpURLConnection
con.connectTimeout = 5 * 1000
con.readTimeout = 10 * 1000
bitmap = BitmapFactory.decodeStream(con.inputStream)
} catch (e: Exception) {
e.printStackTrace()
} finally {
con?.disconnect()
}
return bitmap
}
}
先得到URL（我的是假数据），然后从缓存获取对应的图片，如果为空，就用上面的类重新下载
var url: String = imgData.get(Random().nextInt(imgData.size))
val drawable = lruCache?.get(url)
if (drawable != null) {
holder.iv_pic.setImageDrawable(drawable)
} else {
val task: BitmapWorkerTask = BitmapWorkerTask(holder.iv_pic);
task.execute(url);
}如果使用okhttp，下载代码还可以这样写
首先一个网络连接类
import java.io.InputStream;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
public class OkHttpUtils {
public static InputStream getInputStrem(String url) {
OkHttpClient client = new OkHttpClient();
//2. 创建请求的Request 对象
Request request = new Request.Builder()
.url(url)
.build();
//3. 在Okhttp中创建Call 对象，将request和Client进行绑定
//4. 执行Call对象（call 是interface 实际执行的是RealCall）中的`execute`方法
try {
Response response = client.newCall(request).execute();
return response.body().byteStream();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}异步类（之前的下载类）
inner class BitmapWorkerTask(private val mImageView: ImageView?) : AsyncTask<String, Void, BitmapDrawable>() {
override fun doInBackground(vararg params: String): BitmapDrawable {
val imageUrl = params[0]
// 在后台开始下载图片
val bitmap = downloadBitmap(imageUrl)
val drawable = BitmapDrawable(App.getContext().resources, bitmap)
addBitmapToMemoryCache(imageUrl, drawable)
return drawable
}
override fun onPostExecute(drawable: BitmapDrawable?) {
if (mImageView != null && drawable != null) {
mImageView.setImageDrawable(drawable)
}
}
/**
* 建立HTTP请求，并获取Bitmap对象。
*
* @param imageUrl 图片的URL地址
* @return 解析后的Bitmap对象
*/
private fun downloadBitmap(imageUrl: String): Bitmap? {
return BitmapFactory.decodeStream(OkHttpUtils.getInputStrem(imageUrl))
}
}